Congestive heart failure (CHF) is a widespread and seriously debilitating condition in which the heart fails to pump sufficient blood to meet the body's demand. Heart failure often results in reduced exercise tolerance, higher incidents of ventricular arrhythmia, and shortened life expectancy. It is believed that about five million Americans presently suffer from heart failure, and it is known that heart failure is the most frequent cause for hospitalization among the elderly. Heart failure costs the U.S. healthcare system approximately $38 billion annually, and this figure continues to grow as the population ages.
By tracking the contractile status of the patient's heart, the early onset of CHF can be identified and/or the progression of CHF can be monitored. Each heartbeat in a patient is triggered by a change in the calcium levels of the heart's muscle cells (called “myocytes”). More particularly, contraction and relaxation of the heart are controlled by regulation of intracellular calcium in the myocardium. As the heart ages, it generally becomes less efficiently able to pump blood, particularly during periods of exertion or exercise. This phenomenon results in part from impairment of calcium release and/or calcium uptake by the sarcoplasmic reticulum in each myocyte. Calcium regulation is therefore directly related to the contractile ability of the heart, and is a good indicator of ventricular contractile status.
Monitoring a patient's intracellular calcium regulation is therefore beneficial in diagnosing cardiac health, but tools to provide a diagnostic have not been available. Although several techniques have attempted to observe intracellular calcium regulation in the left ventricle, difficulties have arisen in practice in assessing intracellular calcium regulation for the entire heart. Further, although techniques for gauging intracellular calcium regulation have existed for some time, these techniques have been performed while the patient is undergoing an electrophysiological procedure and is not currently available for use in the ambulatory setting. As a result, patients are typically unaware of issues with the regulation of intracellular calcium in their heart. Even following admission to a emergency room, the patient is not likely to have a procedure which would provide insight into the state of intracellular calcium regulation.
Accordingly, it is desirable to create a device and/or technique that is capable of gauging intracellular calcium regulation and contractile status of the heart so that any issues can be quickly and appropriately treated. Further, it is desirable to monitor contractile status within an implantable or other device that can remain with the patient at all times.
Moreover, in a further embodiment it may be desirable to use contractile status to administer a therapy, or to provide another appropriate response to the patient or physician. Such information may also be desirably used to create a technique for optimizing the performance of a pacemaker or other implantable device.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.